How to make the right Mercedes-Benz SLR McLaren in 5 (not so) easy steps

As I mentioned in an earlier post I am not impressed at all by this car. The reason for remembering it was that one of the major drawback was fixed, not by MB but by Ferrari in the new F12berlinetta. No, it's not the engine, it's the gearbox, one of the problems mentioned in the earlier post. This double clutch gearbox is the closest match I know to the SLR specifications.
So let's make a proper super-sport GT.
1) Buy an SLR, preferably with a broken engine and gearbox.
2) Ditch the gearbox, drive-shaft, differential.
3) Mount the new Ferrari F12berlinetta transaxle, if you can buy one.
4) Ditch the engine compressor and the water-to-air intercooler system.
5) Mount an IHI compressor from AMG 32 engines and two turbocompressors which should generate around 1 bar (14.5 psi) of boost and two correctly dimensioned air-to-air intercoolers.
If all works well you will end up with the right SLR, the power numbers should be around 730 HP, and the weight should be 100 kg lighter.
For extra points you could do some extra steps:
6) Change the injection system with a direct injection one.
7) Convert the engine(cam profiles etc.) to run in Miller cycle.
These should lower significantly the fuel consumption and might also increase the performance.
Looks quite easy, isn't it?

Bugatti Veyron

HERESY!!!
...some might say! In the years of Torquemada my tongue would be cut for what I’ll say, ok, my fingers because I’m writing, and then burned in a low octane gasoline.
After spending the GDP of a small country to design a car that cost a fortune, a big one, this car really has some problems, some of them really big, 8 liters big.

• First, the details of the design.

At least for me the combination of the Bugatti signature radiator with the sloped bonnet didn't result in a pleasant shape.

And let’s have a look at the supports of the rear wing. For a million bucks car I would expect a small masterpiece, Porsche did it on the former 911 GT3! Suprisingly Bugatti chosed a pure functional solution. Instead of the cylinder I would expect something made of carbon fiber, aerodynamic, like the forks of modern race bicycles, and instead of the wing fixture, a beautiful CNC piece made of titanium.

• Second, the details of the bodywork.

With its 1888 kg, the Bugatti Veyron is not light, not for a limousine, and not at all for a supercar. But because they wanted to avoid the toy felling of the all carbon fiber cars, aluminium panels were used for the sides and doors as you can see in the “Pur Sang” version. But aluminium is heavier than carbon fiber and at this Veyron can't afford any extra weight. Well I think that there is something which could help them: GLARE, a composite of thin glass fiber and metal (aluminium) sheets bonded together with epoxy. It is widely used in the Airbus A 380 fuselage and has the same characteristics as a normal aluminium sheet, but 25% lighter.

• And now the 8 liters problem, "The engine!"

Of all the possible variants it looks that the Bugatti engineers had chosen the least refined. It’s only strong points are for the artistic impression: a double V configuration a speciality of the VW house. In order to squeeze 1001 HP from the 8 liters engine, four turbochargers were called for help. The problem is that the turbos don’t comes alone, they always bring their best friend, and turbocharged engine's main enemy, turbo lag. And it looks that in this case there is lot of it, as it was noticed in drive tests. In the same time period, the engineers from Porsche were playing with the new VTG turbos for the latest 911 Turbo generation. It looks that Bugatti wasn’t invited at the party. Still, this showed not to be the perfect fix, as the direct comparison between the 911 Turbo and the relatively similar powered Lamborghini Gallardo indicated an advantage for the aspirated engine. Another even more sophisticated option is the sequential turbo. It worked well on the Toyota Supra a decade ago, now it would work better.
It is known that turbochargers works best when they are connected at 3 cylinders, in engines like straight 6, V6, V12, you’ve got the idea. Therefore a V12 would be a better choice than the W16. If somebody might argue that is hard to achieve the required numbers, I think not, neither the engineers from Porsche. Their turbocharged boxer 6 engines from the latest 911 Turbo and 911 GT2 achieve around half the power from half the number of cylinders, 480 respectively 520 HP from a 6 cylinders 3.6 liters engine. Double the numbers and you will end up with a 7.2 liters V12 of 960 respectively 1040 HP. And yes, there are V12 engines with this capacity, like the Mercedes 7.3 liters V12 used in Pagani Zonda. Still, the previous paragraph about the turbos applies here also.
And yes, as the Mercedes SLR, the Bugatti Veyron is using air water intercoolers, so the comments from the SLR applies here also.

Yet, there is another option, dump the turbos completely. Honda is making 120 HP/liter in their S2000 cabriolet from a 2 liters straight 4 engine. If you manage to raise that value to 125 HP/liter you will find that the 8 liters W16 in more than enough. Yet there is an even more appealing solution, which would not require that level of power density: a 1001 Hp 9 liters 18 cylinders proper W (with 3 banks of 6 cylinders). With just 2 cylinders and 1 liter more than the current engine, it would require around 111 Hp/liter, numbers already obtained by numerous engines, to reach the required power level. With this configuration a series of big but light in weight advantages come:

• No more turbo lag.
• No need for the intercooler, and for the rest of the turbo system, results in lower weight and lower aerodynamic drag.
• The magnesium aluminium hybrid engine block currently used by BMW in their straight 6 aspirated gasoline engines could be used to further lower the weight.
• I read somewhere that because of the heat from the turbos, the engine subframe had to be made of steel. Now this is not the case, aluminium or carbon fiber can be used to lower even more the weight.

I am kind of disappointed by the Bugatti Veyron. Yes, it achieved the required numbers (1000+ HP, 400 km/h) but the way they achieved this is brutal to say the least. Not what I would expect from Bugatti.

McLarren Mercedes SLR

Kids! Do your homework!

Rightfully it is considered the GT of supercars. But it is massively flawed by the current philosophy which guides the latest Mercedes designs. Like most of the top brands Mercedes is trying to have performance cars with all the commodities. Unfortunately it looks that their engine team didn’t finished the same universities as the one from BMW, Porsche etc. Therefore they had embraced a less sophisticated way, larger displacement and brute supercharging in order to achieve high performance levels. To an already big engine, at least for V 8’s, 5.5 liters they added a supercharger to raise the numbers to 600+ HP and a useless 800 Nm. It is not that bad but few knows that the charger by itself is eating 100+ HP only for himself. Ok, this is happening only when it is engaged; the engineers knew that you don’t need that power all the time. Still, no points for the design finesse.

How would I do it?

Of course I would start with two turbochargers. But what about the turbo lag? Because the guys from Mercedes have some experience with superchargers it would be a pity to lose it. So why not take a smaller supercharger like the IHI form the AMG 32 engine. It will help the engine up to around 3500 rpm where the turbos will be alive and kicking, ready to take the job. From here you will have the same power will no parasitic loses. Another thing that is just adding weight to the car is the water cooled intercooler. Because you have a two step cooling process (ambient air -> water -> compressed air) the final temperature of the charge will be higher. Some say that there are more parasitic loses in an air to air intercooler because the compressed air path is longer. I just can say that:

• There is a lot of space under the SLR bonnet, and the lateral air fins could do a great job to dump the heat from the intercooler.
• The air to air intercoolers form Porsche 911 Turbo and 911 GT2 are doing a great job.

Therefore my suggestion: Dump them!

Another thing that is killing the mechanical finesse of the car is the lack of a proper gearbox. I wanted to say that automatic gearboxes are not for supercars, but Porsche is showing me that I’m wrong, the 5 speed automatic transmission of the Porsche 911 Type 997 Turbo has better performance in terms of dynamics against the 6 speed manual. But I still consider that a sequential, if not a double clutch gearbox is the way to go. To use the argument that the engine has to much torque is not acceptable. Bugatti did it!

By the way, it's that hard to make a proper progressive ceramic disks brake? Everybody else did it. And what's with that cheap plastic central console?

Porsche Carrera GT

Why? Why not!*

First let’s have a look at the obvious flaws. It doesn’t have a robotized gearbox! The “purists” might argue about this problem but then why it’s used for years in Formula 1 and Rally car racings? Also, playing with 600+ HP by yourself is not an easy task, and there are a lot of complains about the way you start the car from stand-still because it is really easy to kill the engine.

And the second issue is the engine. It was praised by some, but is it that good? It might be, but my guts tell me that it is still a far-cry from what it could be! How? Easy, take an engine and two thirds from Porsche 911 GT3. A summary of the specifications of this engine is: 3.6 liters boxer 6 cylinders, 415 HP. Some math later and we will end with a 6 liters V 10 developing 691 HP. Well it is in another league than the real one: 5.7 liters V 10 developing 615 HP.

In an article I’ve read, it was said that the people will remember this car for long time. I have my doubts.

* Why is not a Full Design? The theme of this blogs sequence.

Full Design

Full Design

Here are some thoughts and ideas about “every-day” objects, specifically about those ones which look underdeveloped, which sometimes are screaming for at least a new iteration in their design to be “fully designed”.

Because I am a car enthusiast in general and addicted to car technology and car design, most of my thoughts will go on that direction.

Of course there is almost nothing in an every-day car that can make you daydream; my focus will be mostly on super cars. Their price tag should guarantee that there is nothing more that you could request from them, that you’ve reached the end of the Car Planet! Unfortunately usually it’s not the case.